If zlib.output_compression is on, then it (sensibly) sends a
Vary: Accept-Encoding
header to the browser. However, if the user's script has sent its own Vary: header, then that header will get clobbered by zlib's. Better solutions would be to either:
* let the user's header take preference, and caution the user to include Accept-Encoding in the custom one, or
* magically combine the user's header and the zlib one.
Refernece: RFC 2616 (HTTP/1.1 Spec), Section 14.44
Sample script:
<?php
ini_set('zlib.output_compression', 'on');
// do something with $_SERVER['HTTP_ACCEPT_LANGUAGE']
header('Vary: Accept-Language');
// output something
?>

Patches

Pull Requests

History

This bug has been fixed in CVS.
In case this was a PHP problem, snapshots of the sources are packaged
every three hours; this change will be in the next snapshot. You can
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In case this was a documentation problem, the fix will show up soon at
http://www.php.net/manual/.
In case this was a PHP.net website problem, the change will show
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Thank you for the report, and for helping us make PHP better.

This bug has been fixed in CVS.
Snapshots of the sources are packaged every three hours; this change will be in the next snapshot. You can grab the snapshot at http://snaps.php.net/.
Sorry, the first fix was only for ob_gzhandler, but now it should be fixed for zlib.output_compression, too.

[2012-12-09 18:09 UTC] mtanalin at yandex dot ru

It seems we still (again?) have this in PHP 5.3 and 5.4. Tested with latest 5.3.19 and 5.4.9.
Testcase:
<?php
header('Vary: X-Requested-With');
ob_start('ob_gzhandler');
echo 'Hello world.';
// As a result, we have wrong `Vary: Accept-Encoding`,
// though we should have `Vary: X-Requested-With,Accept-Encoding`.
For example, when using Ajax, it's quite typical and handy for Ajax and non-Ajax responses to have exactly same URL and differ in just `X-Requested-With` request-header.
To make it possible for user agents to cache such responses separately (IE9 at least uses common cache for Ajax and non-Ajax responses by default), `Vary: X-Requested-With` header should be set, but it's then wrongly _overrided_ (instead of being appended) with `Vary: Accept-Encoding` header set by `ob_start('ob_gzhandler')`.
Currently, we are forced to add headers with `Header add` of Apache web-server instead of PHP itself to workaround this bug of PHP.
Thanks.